Leakage of process piping flanged joints during plant operation is a major problem and challenges maintenance and operations personnel charged with keeping plant equipment operating at peak efficiency. In many cases, leaking flanges pose safety and environmental concerns leading to plant shutdown. Numerous factors can contribute to a leaking flanged joint. These factors include: insufficient bolt loading, poor flange alignment, improper gasket selection or an improper surface finish or dimensional preparation of the gasket-sealing surface on the flange. Many new practices have been developed and employed over the years to improve the reliability of the flange joint including new gasket materials, improved bolting practices and spring type washers.
However, regardless of the training and engineering practices implemented to ensure reliable performance of flange joints, failures still occur. When bringing the system down is not financially feasible, methods for sealing the leak while the pipe remains pressurized have been effectively utilized to stop most leaks. These methods hydraulically inject viscous sealing compounds into a secondary pressure vessel while the flange joint remains under system pressure and temperature.
These hydraulic injection methods have several implementation and design engineering drawbacks. The secondary pressure vessel must undergo detailed engineering design review to ensure the structural stability. Moreover, each leak presents different problems, e.g., the size of the leak, pressure criteria and pipe sizes; thus, secondary pressure vessels are not portable from one flange to the next. Highly trained and experienced specialty contract personnel are required to evaluate the problem, to design a solution and to fabricate and install the necessary hardware. In cases where the flange gap is very small or inconsistent, these methods frequently impart physical damage to the flanges, including mechanical peening to close gaps, and drilling and tapping of holes into the flanges for injection ports. Utilization of these methods frequently lead to major refurbishment or replacement of the flanges during the subsequent shutdown, which can be difficult, time consuming and expensive. Lastly, there is the potential for the injection of sealing compounds into the process system, which can cause entire system shutdowns.
Accordingly, there is a need in the art for a non-invasive method and apparatus for sealing a leaking pressurized flange joint.